The present invention relates to a throttle-valve setting device which has a throttle valve setting lever which is connected to an accelerator pedal and actuates a throttle valve arranged, fixed for rotation, on a throttle valve shaft, the invention including a setting motor operating exclusively in the opening direction of the throttle valve against the force of a return spring in order to permit idling adjustment.
Such throttle valve setting devices are provided in modern motor vehicles and are therefore known.
In today's motor vehicles the internal combustion engine must produce different torques also upon idling. The power required, for example, increases when the air conditioner of a motor vehicle is to operate upon idling. When the internal combustion engine is cold, more energy is required in order to keep it operating than when the internal combustion engine is warm. In order to be able to keep the idling speed of rotation as low as possible under such different conditions, idling adjustment is being provided more and more generally. In such case, the throttle valve can be opened by means of the setting motor to a greater or lesser extent within a stipulated operating range without the driver having to actuate the accelerator pedal for this.
The known idling controls have the disadvantage of their behavior upon failure of the energy actuating their setting motor. Ordinarily, the idling adjustment is designed in the manner that the throttle valve is swung, by a setting spring, into a position in which the idling speed of rotation reaches the upper value of the operating range available for the idling control. In practice, such high idling speeds of rotation induce an automatic transmission to enter into gear. If the idling control is developed in such a manner that, upon a failure of the external energy, the throttle valve reaches its substantially closed final position, then the internal combustion engine generally stalls upon idling, which is a nuisance and disadvantage for safety in travel.